Author: Frédéric Bertrand

# plsRglm: Historical Applications and Algorithmic Notes

#### Frédéric Bertrand

#### Jérémy Magnanensi

#### Nicolas Meyer

#### Myriam Maumy-Bertrand

#### Historical applications note refreshed March 2026

This vignette preserves the structure of the package’s historical applications note while updating the code examples and summaries to the current `plsRglm` interfaces. It is the companion to the main getting-started vignette and focuses on the longer case studies that motivated the package.

By default, the chunks are shown but not executed. To rerun the analyses while rendering, set:

    options(plsRglm.rebuild_vignette = TRUE)

before calling `rmarkdown::render()`. Some sections also require optional packages such as `chemometrics` and `xtable`.

> The aim of the `plsRglm` package is to deal with incomplete, as well as complete, data sets through several techniques that had not previously been implemented together in R: bootstrap confidence intervals, repeated k-fold cross-validation, and partial least squares regression for generalized linear models.

# Motivation

The analysis of data sets with many strongly correlated predictors is common in medicine, biology, chemometrics, and related fields. Classical least-squares regression is often not adequate when predictors are highly collinear, when there are more predictors than subjects, or when missing values are present. Partial least squares regression (PLSR) addresses part of this problem by constructing latent components that summarize the predictor space while remaining informative about the response.

Existing R software already implemented several variants of PLSR, but the original `plsRglm` vignette emphasized several gaps that this package set out to fill:

- support for incomplete data in the predictor matrix,
- generalized linear model extensions of PLSR,
- repeated cross-validation using multiple criteria,
- bootstrap confidence intervals and significance assessment on the original predictors,
- weighted low-level constructors via `PLS_lm_wvc()` and `PLS_glm_wvc()`.

The package was developed around several motivating applications, including the Cornell mixture data, pine caterpillar studies, allelotyping data with missing values, and Bordeaux wine quality data.

# Theory

## PLS Regression

For more detailed introductions to PLS regression, see Hoskuldsson (1988) and Wold et al. (2001). In the classical PLSR setting, let `y` be the response variable and `X` the centered and scaled matrix of predictors. The method constructs orthogonal components `t_1, ..., t_H` as linear combinations of the original predictors. If `T` denotes the matrix of retained components, the model can be written as:

\[ y = T c + \varepsilon, \]

and, since the components can themselves be expressed from the original predictors through a weight matrix \(W^\ast\),

\[ y = X W^\ast c + \varepsilon. \]

Expanding the right-hand side shows how the original predictors contribute to the fitted response through the component coefficients.

Scaling is often used, as in PCA, to balance the influence of each predictor. In practice, however, centered but unscaled predictors can also be used when that is scientifically more appropriate.

## PLS Generalized Linear Regression

One of the main contributions of `plsRglm` is the extension of PLSR to generalized linear regression models. In this setting, the response can be continuous, binary, ordinal, count-valued, or belong to another GLM family. The linear predictor is built from the latent PLS components:

\[ g(\theta_i) = \sum_{h=1}^H c_h \sum_{j=1}^p w^\ast_{jh} x_{ij}, \]

where \(g\) is the link function associated with the chosen response family.

The key difficulty is that, unlike in ordinary PLSR, residual-based updates cannot be obtained from a sequence of ordinary linear regressions on the response. The original vignette therefore stressed two implementation ideas:

1. at step \(h\), fit a GLR of `y` on the existing components and each candidate predictor in turn;
2. ensure orthogonality of the next component by computing residualized predictors through ordinary least-squares regressions on the previously constructed components.

The algorithm implemented in the package follows this structure:

1. Center and scale the predictors.
2. Build the first component from the univariate GLR coefficients of `y` on each predictor.
3. For the second and subsequent components, regress each predictor on the previously found components, retain the residualized predictors, and compute the next component from the corresponding GLR coefficients.
4. Express each component both in terms of the residualized design matrix and in terms of the original predictors.

This construction also works with incomplete predictor matrices, because each individual component score can be computed from the available coordinates only.

## Stopping Criteria

The package exposes several criteria for choosing the number of components:

- AIC and BIC,
- cross-validated \(Q^2\)-style criteria,
- miss-classification counts for binary and ordinal responses,
- the “no more significant predictor” stopping rule described by Bastien et al. (2005).

For complete-data PLSR models, corrected degrees-of-freedom criteria from Kramer and Sugiyama (2011) are also available; in the other cases the package falls back to naive degrees-of-freedom calculations.

## Bootstrap

The applications note distinguishes two bootstrap strategies that are available both for PLSR and PLSGLR:

- bootstrap on `(y, X)`,
- bootstrap on `(y, T)`.

The `(y, X)` approach resamples the original response-predictor pairs and refits the model repeatedly. The `(y, T)` approach resamples the response together with the retained latent components, keeping the mapping from components back to the original predictors fixed. The latter is usually faster and more stable, especially for generalized linear models. In current package defaults, `bootpls()` starts with `(y, X)` resampling while `bootplsglm()` starts with `(y, T)` resampling.

The implementation is built on top of `boot::boot()`, which means that different bootstrap schemes such as ordinary, balanced, permutation, or antithetic resampling can be forwarded through the package API.

# Applications

## Data

The package contains several datasets used throughout the original vignette:

- `Cornell`, from Kettaneh-Wold (1992),
- `pine`, for the pine processionary caterpillar study,
- `aze` and `aze_compl`, for the allelotyping application,
- `bordeaux`, for Bordeaux wine quality.

The original PDF also used the `hyptis` dataset from `chemometrics` and the base `rock` dataset.

## PLS Regression: Cornell

The Cornell example uses the formula interface of `plsR()` and illustrates cross-validation, bootstrap on `(y, X)`, bootstrap on `(y, T)`, and the `signpred()` summary of variable significance across plausible component counts.

    data(Cornell)

    cv.modpls <- cv.plsR(Y ~ ., data = Cornell, nt = 6, K = 6)
    res.cv.modpls <- cvtable(summary(cv.modpls))

    res6 <- plsR(Y ~ ., data = Cornell, nt = 6, typeVC = "standard", pvals.expli = TRUE)
    colSums(res6$pvalstep)
    res6$InfCrit

    res6 <- plsR(Y ~ ., data = Cornell, nt = 6, pvals.expli = TRUE)
    colSums(res6$pvalstep)

The original vignette then repeated the 6-fold cross-validation 100 times and used the empirical distribution of retained component counts as a weighting device in later bootstrap-based significance summaries.

    set.seed(123)
    cv.modpls <- cv.plsR(
      Y ~ .,
      data = Cornell,
      nt = 6,
      K = 6,
      NK = 100,
      random = TRUE,
      verbose = FALSE
    )
    res.cv.modpls <- cvtable(summary(cv.modpls))
    plot(res.cv.modpls)

The selected model in the PDF retained one component for the final fit.

    res <- plsR(Y ~ ., data = Cornell, nt = 1, pvals.expli = TRUE)
    res
    res$wwetoile
    biplot(res6$tt, res6$pp)

    modpls2 <- plsR(Y ~ ., data = Cornell, 6, sparse = TRUE)
    modpls3 <- plsR(Y ~ ., data = Cornell, 6, sparse = TRUE, sparseStop = FALSE)

### Bootstrap `(y, X)`

    set.seed(123)
    Cornell.bootYX1 <- bootpls(res, R = 1000, verbose = FALSE)

    boxplots.bootpls(Cornell.bootYX1, indice = 2:8)
    temp.ci <- confints.bootpls(Cornell.bootYX1, indice = 2:8)
    plots.confints.bootpls(
      temp.ci,
      typeIC = "BCa",
      colIC = c("blue", "blue", "blue", "blue"),
      legendpos = "topright"
    )

    plot(Cornell.bootYX1, index = 2, jack = TRUE)
    car::dataEllipse(
      Cornell.bootYX1$t[, 2],
      Cornell.bootYX1$t[, 3],
      cex = 0.3,
      levels = c(0.5, 0.95, 0.99),
      robust = TRUE,
      xlab = "X2",
      ylab = "X3"
    )

### Bootstrap `(y, T)`

    set.seed(123)
    Cornell.bootYT1 <- bootpls(res, typeboot = "fmodel_np", R = 1000)
    boxplots.bootpls(Cornell.bootYT1, indices = 2:8)

    temp.ci <- confints.bootpls(Cornell.bootYT1, indices = 2:8)
    plots.confints.bootpls(
      temp.ci,
      typeIC = "BCa",
      colIC = c("blue", "blue", "blue", "blue"),
      legendpos = "topright"
    )

    res2 <- plsR(Y ~ ., data = Cornell, nt = 2)
    Cornell.bootYT2 <- bootpls(res2, typeboot = "fmodel_np", R = 1000)
    temp.ci2 <- confints.bootpls(Cornell.bootYT2, indices = 2:8)

    ind.BCa.CornellYT1 <- confints2signifind(temp.ci, typeIC = "BCa")
    ind.BCa.CornellYT2 <- confints2signifind(temp.ci2, typeIC = "BCa")

    matind <- rbind(YT1 = ind.BCa.CornellYT1, YT2 = ind.BCa.CornellYT2)
    pi.e <- weighted_significance(res.cv.modpls$CVQ2, matind)

    signpred(t(matind), labsize = 0.5, plotsize = 12)
    text(1:(ncol(matind)) - 0.5, -0.5, pi.e, cex = 1.4)
    mtext(expression(pi[e]), side = 2, las = 1, line = 2, at = -0.5, cex = 1.4)

## PLS Binary Logistic Regression: Microsatellites

This section reproduces the original allelotyping workflow on both the incomplete dataset `aze` and the imputed dataset `aze_compl`.

### Method and Results: Original Dataset

    data(aze)
    Xaze <- aze[, 2:34]
    yaze <- aze$y

The original PDF first ran an 8-fold cross-validation with up to 10 components, then repeated it 100 times to stabilize the choice of the final model.

    cv.modpls <- cv.plsRglm(
      object = yaze,
      dataX = Xaze,
      nt = 10,
      modele = "pls-glm-logistic",
      K = 8
    )
    res.cv.modpls <- cvtable(summary(cv.modpls, MClassed = TRUE))

    res10 <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-logistic", pvals.expli = TRUE)
    colSums(res10$pvalstep)

    modpls2 <- plsRglm(
      dataY = yaze,
      dataX = Xaze,
      nt = 10,
      modele = "pls-glm-logistic",
      sparse = TRUE,
      sparseStop = TRUE
    )

    set.seed(123)
    cv.modpls.logit <- cv.plsRglm(
      object = yaze,
      dataX = Xaze,
      nt = 10,
      modele = "pls-glm-logistic",
      K = 8,
      NK = 100
    )
    res.cv.modpls.logit <- cvtable(summary(cv.modpls.logit, MClassed = TRUE))
    plot(res.cv.modpls.logit)

The legacy vignette kept four components for the final logistic model.

    res <- plsRglm(yaze, Xaze, nt = 4, modele = "pls-glm-logistic", pvals.expli = TRUE)
    res
    res$wwetoile
    biplot(res$tt, res$pp)

    modpls3 <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-logistic", sparse = FALSE, pvals.expli = TRUE)
    modpls4 <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-logistic", sparse = TRUE, pvals.expli = TRUE)

#### Bootstrap `(y, X)`

    set.seed(123)
    aze.bootYX4 <- bootplsglm(res, typeboot = "plsmodel", R = 1000, verbose = FALSE)

    boxplots.bootpls(aze.bootYX4, las = 2, mar = c(5, 2, 1, 1) + 0.1)
    temp.ci <- confints.bootpls(aze.bootYX4)
    plots.confints.bootpls(
      temp.ci,
      typeIC = "BCa",
      colIC = c("blue", "blue", "blue", "blue"),
      legendpos = "topright",
      las = 2,
      mar = c(5, 2, 1, 1) + 0.1
    )

#### Bootstrap `(y, T)`

    set.seed(123)
    aze.bootYT4 <- bootplsglm(res, R = 1000, verbose = FALSE)

    boxplots.bootpls(aze.bootYT4, las = 2, mar = c(5, 2, 1, 1) + 0.1)
    temp.ci4 <- confints.bootpls(aze.bootYT4)
    plots.confints.bootpls(
      temp.ci4,
      typeIC = "BCa",
      colIC = c("blue", "blue", "blue", "blue"),
      legendpos = "topright",
      las = 2,
      mar = c(5, 2, 1, 1) + 0.1
    )

    res1 <- plsRglm(yaze, Xaze, nt = 1, modele = "pls-glm-logistic")
    res2 <- plsRglm(yaze, Xaze, nt = 2, modele = "pls-glm-logistic")
    res3 <- plsRglm(yaze, Xaze, nt = 3, modele = "pls-glm-logistic")
    res5 <- plsRglm(yaze, Xaze, nt = 5, modele = "pls-glm-logistic")
    res6 <- plsRglm(yaze, Xaze, nt = 6, modele = "pls-glm-logistic")
    res7 <- plsRglm(yaze, Xaze, nt = 7, modele = "pls-glm-logistic")
    res8 <- plsRglm(yaze, Xaze, nt = 8, modele = "pls-glm-logistic")

    aze.bootYT1 <- bootplsglm(res1, R = 1000)
    aze.bootYT2 <- bootplsglm(res2, R = 1000)
    aze.bootYT3 <- bootplsglm(res3, R = 1000)
    aze.bootYT5 <- bootplsglm(res5, R = 1000)
    aze.bootYT6 <- bootplsglm(res6, R = 1000)
    aze.bootYT7 <- bootplsglm(res7, R = 1000)
    aze.bootYT8 <- bootplsglm(res8, R = 1000)

    temp.ci1 <- confints.bootpls(aze.bootYT1)
    temp.ci2 <- confints.bootpls(aze.bootYT2)
    temp.ci3 <- confints.bootpls(aze.bootYT3)
    temp.ci5 <- confints.bootpls(aze.bootYT5)
    temp.ci6 <- confints.bootpls(aze.bootYT6)
    temp.ci7 <- confints.bootpls(aze.bootYT7)
    temp.ci8 <- confints.bootpls(aze.bootYT8)

    ind.BCa.azeYT1 <- confints2signifind(temp.ci1, typeIC = "BCa")
    ind.BCa.azeYT2 <- confints2signifind(temp.ci2, typeIC = "BCa")
    ind.BCa.azeYT3 <- confints2signifind(temp.ci3, typeIC = "BCa")
    ind.BCa.azeYT4 <- confints2signifind(temp.ci4, typeIC = "BCa")
    ind.BCa.azeYT5 <- confints2signifind(temp.ci5, typeIC = "BCa")
    ind.BCa.azeYT6 <- confints2signifind(temp.ci6, typeIC = "BCa")
    ind.BCa.azeYT7 <- confints2signifind(temp.ci7, typeIC = "BCa")
    ind.BCa.azeYT8 <- confints2signifind(temp.ci8, typeIC = "BCa")

    matind <- rbind(
      YT1 = ind.BCa.azeYT1,
      YT2 = ind.BCa.azeYT2,
      YT3 = ind.BCa.azeYT3,
      YT4 = ind.BCa.azeYT4,
      YT5 = ind.BCa.azeYT5,
      YT6 = ind.BCa.azeYT6,
      YT7 = ind.BCa.azeYT7,
      YT8 = ind.BCa.azeYT8
    )

    pi.e <- weighted_significance(res.cv.modpls.logit$CVMC, matind)
    signpred(t(matind), labsize = 2, plotsize = 12)
    text(1:(ncol(matind)) - 0.5, -1, pi.e, cex = 0.5)
    mtext(expression(pi[e]), side = 2, las = 1, line = 2, at = -1)

### Specifying Families, Links, or Custom GLRs

The original vignette showed that `modele = "pls-glm-logistic"` is a convenience shortcut for `modele = "pls-glm-family"` together with `family = binomial(link = logit)`.

    modpls <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-logistic", MClassed = TRUE, pvals.expli = TRUE)
    modpls2 <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-family", family = binomial(link = "logit"), MClassed = TRUE, pvals.expli = TRUE)
    modpls3 <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-family", family = binomial(link = "probit"), MClassed = TRUE, pvals.expli = TRUE)
    modpls4 <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-family", family = binomial(link = "cauchit"), MClassed = TRUE, pvals.expli = TRUE)
    modpls5 <- plsRglm(yaze, Xaze, nt = 10, modele = "pls-glm-family", family = binomial(link = "cloglog"), MClassed = TRUE, pvals.expli = TRUE)

    set.seed(123)
    cv.modpls.probit <- cv.plsRglm(object = yaze, dataX = Xaze, nt = 10, modele = "pls-glm-family", family = binomial(link = "probit"), K = 8, NK = 100)
    cv.modpls.cauchit <- cv.plsRglm(object = yaze, dataX = Xaze, nt = 10, modele = "pls-glm-family", family = binomial(link = "cauchit"), K = 8, NK = 100)
    cv.modpls.cloglog <- cv.plsRglm(object = yaze, dataX = Xaze, nt = 10, modele = "pls-glm-family", family = binomial(link = "cloglog"), K = 8, NK = 100)

    res.cv.modpls.probit <- cvtable(summary(cv.modpls.probit, MClassed = TRUE))
    res.cv.modpls.cauchit <- cvtable(summary(cv.modpls.cauchit, MClassed = TRUE))

    layout(matrix(1:4, nrow = 2))
    plot(res.cv.modpls.logit)
    plot(res.cv.modpls.probit)
    plot(res.cv.modpls.cauchit)
    layout(1)

### Method and Results: Imputed Dataset

    data(aze_compl)
    Xaze_compl <- aze_compl[, 2:34]
    yaze_compl <- aze_compl$y

    cv.modpls_compl <- cv.plsRglm(
      object = yaze_compl,
      dataX = Xaze_compl,
      nt = 10,
      modele = "pls-glm-logistic",
      K = 8
    )
    res.cv.modpls_compl <- cvtable(summary(cv.modpls_compl, MClassed = TRUE))

    set.seed(123)
    cv.modpls_compl <- cv.plsRglm(
      object = yaze_compl,
      dataX = Xaze_compl,
      nt = 10,
      modele = "pls-glm-logistic",
      K = 8,
      NK = 100
    )
    res.cv.modpls_compl <- cvtable(summary(cv.modpls_compl, MClassed = TRUE))
    plot(res.cv.modpls_compl)

    res_compl <- plsRglm(yaze_compl, Xaze_compl, nt = 3, modele = "pls-glm-logistic", pvals.expli = TRUE)
    res_compl

    aze_compl.bootYX3 <- bootplsglm(res_compl, typeboot = "plsmodel", R = 1000, verbose = FALSE)
    boxplots.bootpls(aze_compl.bootYX3, las = 2, mar = c(5, 2, 1, 1) + 0.1)
    temp.ci <- confints.bootpls(aze_compl.bootYX3)
    plots.confints.bootpls(temp.ci, typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright", las = 2, mar = c(5, 2, 1, 1) + 0.1)

    aze_compl.bootYT3 <- bootplsglm(res_compl, R = 1000, verbose = FALSE)
    boxplots.bootpls(aze_compl.bootYT3, las = 2, mar = c(5, 2, 1, 1) + 0.1)
    temp.ci3 <- confints.bootpls(aze_compl.bootYT3)
    plots.confints.bootpls(temp.ci3, typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright", las = 2, mar = c(5, 2, 1, 1) + 0.1)

## PLS Regression Bis: Pine Caterpillar

The pine example is the second linear-regression case study in the original vignette. It also illustrates incomplete predictors and different cross-validation prediction rules.

    data(pine)
    Xpine <- pine[, 1:10]
    ypine <- pine[, 11]

    cv.modpls <- cv.plsR(ypine, Xpine, nt = 10)
    res.cv.modpls <- cvtable(summary(cv.modpls))

    res1 <- plsR(ypine, Xpine, nt = 10, typeVC = "standard", pvals.expli = TRUE)
    colSums(res1$pvalstep)
    res1$InfCrit

    set.seed(123)
    cv.modpls <- cv.plsR(x11 ~ ., data = pine, nt = 10, NK = 100)
    res.cv.modpls <- cvtable(summary(cv.modpls))
    plot(res.cv.modpls)

    res <- plsR(x11 ~ ., data = pine, nt = 1, pvals.expli = TRUE)
    res
    biplot(res1$tt, res1$pp)

    data(pine_full)
    Xpine_full <- pine_full[, 1:10]
    ypine_full <- pine_full[, 11]
    modpls5 <- plsR(log(ypine_full), Xpine_full, 1)

    XpineNAX21 <- Xpine
    XpineNAX21[1, 2] <- NA
    modpls6 <- plsR(ypine, XpineNAX21, 4)
    modpls6$YChapeau[1, ]
    plsR(ypine, XpineNAX21, 2, dataPredictY = XpineNAX21[1, ])$ValsPredictY

    modpls7 <- plsR(ypine, XpineNAX21, 4, EstimXNA = TRUE)
    modpls7$XChapeau
    modpls7$XChapeauNA

    plsR(ypine, Xpine, 10, typeVC = "none")$InfCrit
    plsR(ypine, Xpine, 10, typeVC = "standard")$InfCrit
    plsR(ypine, Xpine, 10, typeVC = "adaptative")$InfCrit
    plsR(ypine, Xpine, 10, typeVC = "missingdata")$InfCrit
    plsR(ypine, XpineNAX21, 10, typeVC = "none")$InfCrit
    plsR(ypine, XpineNAX21, 10, typeVC = "standard")$InfCrit
    plsR(ypine, XpineNAX21, 10, typeVC = "adaptative")$InfCrit
    plsR(ypine, XpineNAX21, 10, typeVC = "missingdata")$InfCrit

### Bootstrap `(y, X)` and `(y, T)`

    set.seed(123)
    Pine.bootYX1 <- bootpls(res, R = 1000)
    boxplots.bootpls(Pine.bootYX1, indice = 2:11)
    temp.ci <- confints.bootpls(Pine.bootYX1, indice = 2:11)
    plots.confints.bootpls(temp.ci, typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright")
    plot(Pine.bootYX1, index = 2, jack = TRUE)
    car::dataEllipse(Pine.bootYX1$t[, 2], Pine.bootYX1$t[, 3], cex = 0.3, levels = c(0.5, 0.95, 0.99), robust = TRUE, xlab = "X2", ylab = "X3")

    set.seed(123)
    Pine.bootYT1 <- bootpls(res, typeboot = "fmodel_np", R = 1000)
    boxplots.bootpls(Pine.bootYT1, indices = 2:11)
    temp.ci <- confints.bootpls(Pine.bootYT1, indices = 2:11)
    plots.confints.bootpls(temp.ci, typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright")

## PLS Ordinal Logistic Regression: Bordeaux Wine Quality

The Bordeaux section in the original PDF also appears in condensed form in the package README.

    set.seed(12345)
    data(bordeaux)
    bordeaux$Quality <- factor(bordeaux$Quality, ordered = TRUE)

    modpls1 <- plsRglm(Quality ~ ., data = bordeaux, 4, modele = "pls-glm-polr", pvals.expli = TRUE)
    modpls1

    Xbordeaux <- bordeaux[, 1:4]
    ybordeaux <- bordeaux$Quality
    modpls2 <- plsRglm(ybordeaux, Xbordeaux, 4, modele = "pls-glm-polr", pvals.expli = TRUE)
    modpls2

    all(modpls1$InfCrit == modpls2$InfCrit)
    colSums(modpls2$pvalstep)

    set.seed(123)
    cv.modpls <- cv.plsRglm(ybordeaux, Xbordeaux, nt = 4, modele = "pls-glm-polr", NK = 100, verbose = FALSE)
    res.cv.modpls <- cvtable(summary(cv.modpls, MClassed = TRUE))
    plot(res.cv.modpls)

    res <- plsRglm(ybordeaux, Xbordeaux, 1, modele = "pls-glm-polr")
    res$FinalModel
    biplot(modpls1$tt, modpls1$pp)

    XbordeauxNA <- Xbordeaux
    XbordeauxNA[1, 1] <- NA
    modplsNA <- plsRglm(ybordeaux, XbordeauxNA, 4, modele = "pls-glm-polr")
    modplsNA
    data.frame(formula = modpls1$Coeffs, datasets = modpls2$Coeffs, datasetsNA = modplsNA$Coeffs)

### Bootstrap `(y, X)`

    options(contrasts = c("contr.treatment", "contr.poly"))

    modplsglm3 <- plsRglm(ybordeaux, Xbordeaux, 1, modele = "pls-glm-polr")
    bordeaux.bootYT <- bootplsglm(modplsglm3, sim = "permutation", R = 250, verbose = FALSE)
    boxplots.bootpls(bordeaux.bootYT)
    boxplots.bootpls(bordeaux.bootYT, ranget0 = TRUE)

    bordeaux.bootYX1 <- bootplsglm(res, typeboot = "plsmodel", sim = "balanced", R = 1000, verbose = FALSE)
    boxplots.bootpls(bordeaux.bootYX1)
    temp.ci <- confints.bootpls(bordeaux.bootYX1)
    plots.confints.bootpls(temp.ci, typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright")

    bordeaux.bootYX1strata <- bootplsglm(res, typeboot = "plsmodel", sim = "balanced", R = 1000, strata = unclass(ybordeaux), verbose = FALSE)
    boxplots.bootpls(bordeaux.bootYX1strata)
    confints.bootpls(bordeaux.bootYX1strata)
    plots.confints.bootpls(confints.bootpls(bordeaux.bootYX1strata), typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright")

### Bootstrap `(y, T)`

    bordeaux.bootYT1 <- bootplsglm(res, sim = "balanced", R = 1000, verbose = FALSE)
    boxplots.bootpls(bordeaux.bootYT1)
    temp.ci <- confints.bootpls(bordeaux.bootYT1)
    plots.confints.bootpls(temp.ci, typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright")

    bordeaux.bootYT1strata <- bootplsglm(res, sim = "balanced", R = 1000, strata = unclass(ybordeaux), verbose = FALSE)
    boxplots.bootpls(bordeaux.bootYT1strata)
    temp.cis <- confints.bootpls(bordeaux.bootYT1strata)
    plots.confints.bootpls(temp.cis, typeIC = "BCa", colIC = c("blue", "blue", "blue", "blue"), legendpos = "topright")

    res2 <- plsRglm(ybordeaux, Xbordeaux, 2, modele = "pls-glm-polr", verbose = FALSE)
    res3 <- plsRglm(ybordeaux, Xbordeaux, 3, modele = "pls-glm-polr", verbose = FALSE)
    res4 <- plsRglm(ybordeaux, Xbordeaux, 4, modele = "pls-glm-polr", verbose = FALSE)

    bordeaux.bootYT2 <- bootplsglm(res2, sim = "balanced", R = 1000, verbose = FALSE)
    bordeaux.bootYT3 <- bootplsglm(res3, sim = "balanced", R = 1000, verbose = FALSE)
    bordeaux.bootYT4 <- bootplsglm(res4, sim = "balanced", R = 1000, verbose = FALSE)
    bordeaux.bootYT2s <- bootplsglm(res2, sim = "balanced", R = 1000, strata = unclass(ybordeaux), verbose = FALSE)
    bordeaux.bootYT3s <- bootplsglm(res3, sim = "balanced", R = 1000, strata = unclass(ybordeaux), verbose = FALSE)
    bordeaux.bootYT4s <- bootplsglm(res4, sim = "balanced", R = 1000, strata = unclass(ybordeaux), verbose = FALSE)

    temp.ci2 <- confints.bootpls(bordeaux.bootYT2)
    temp.ci3 <- confints.bootpls(bordeaux.bootYT3)
    temp.ci4 <- confints.bootpls(bordeaux.bootYT4)
    temp.cis2 <- confints.bootpls(bordeaux.bootYT2s)
    temp.cis3 <- confints.bootpls(bordeaux.bootYT3s)
    temp.cis4 <- confints.bootpls(bordeaux.bootYT4s)

    ind.BCa.bordeauxYT1 <- confints2signifind(temp.ci, typeIC = "BCa")
    ind.BCa.bordeauxYT2 <- confints2signifind(temp.ci2, typeIC = "BCa")
    ind.BCa.bordeauxYT3 <- confints2signifind(temp.ci3, typeIC = "BCa")
    ind.BCa.bordeauxYT4 <- confints2signifind(temp.ci4, typeIC = "BCa")
    ind.BCa.bordeauxYT1s <- confints2signifind(temp.cis, typeIC = "BCa")
    ind.BCa.bordeauxYT2s <- confints2signifind(temp.cis2, typeIC = "BCa")
    ind.BCa.bordeauxYT3s <- confints2signifind(temp.cis3, typeIC = "BCa")
    ind.BCa.bordeauxYT4s <- confints2signifind(temp.cis4, typeIC = "BCa")

    matind <- rbind(YT1 = ind.BCa.bordeauxYT1, YT2 = ind.BCa.bordeauxYT2, YT3 = ind.BCa.bordeauxYT3, YT4 = ind.BCa.bordeauxYT4)
    pi.e <- weighted_significance(res.cv.modpls$CVMC, matind)
    signpred(t(matind), labsize = 0.5, plotsize = 12)
    mtext(expression(pi[e]), side = 2, las = 1, line = 2, at = -0.3, cex = 1.4)
    text(1:(ncol(matind)) - 0.5, -0.3, pi.e, cex = 1.4)
    text(1:(ncol(matind)) - 0.5, -0.75, c("Temp", "Sun", "Heat", "Rain"), cex = 1.4)

    matinds <- rbind(YT1 = ind.BCa.bordeauxYT1s, YT2 = ind.BCa.bordeauxYT2s, YT3 = ind.BCa.bordeauxYT3s, YT4 = ind.BCa.bordeauxYT4s)
    pi.es <- weighted_significance(res.cv.modpls$CVMC, matinds)
    signpred(t(matinds), pred.lablength = 10, labsize = 0.5, plotsize = 12)
    mtext(expression(pi[e]), side = 2, las = 1, line = 2, at = -0.3, cex = 1.4)
    text(1:(ncol(matinds)) - 0.5, -0.3, pi.es, cex = 1.4)
    text(1:(ncol(matinds)) - 0.5, -0.75, c("Temp", "Sun", "Heat", "Rain"), cex = 1.4)

## PLS Ordinal Logistic Regression: Hyptis

This section requires the optional `chemometrics` package.

    data("hyptis", package = "chemometrics")
    yhyptis <- factor(hyptis$Group, ordered = TRUE)
    Xhyptis <- as.data.frame(hyptis[, 1:6])

    modpls <- plsRglm(yhyptis, Xhyptis, 6, modele = "pls-glm-polr", pvals.expli = TRUE)
    modpls
    colSums(modpls$pvalstep)

    set.seed(123)
    cv.modpls <- cv.plsRglm(object = yhyptis, dataX = Xhyptis, nt = 4, K = 5, NK = 100, modele = "pls-glm-polr")
    res.cv.modpls <- cvtable(summary(cv.modpls, MClassed = TRUE))
    plot(res.cv.modpls)

    modpls2 <- plsRglm(yhyptis, Xhyptis, 3, modele = "pls-glm-polr")
    modpls2
    table(yhyptis, predict(modpls2$FinalModel, type = "class"))
    biplot(modpls2$tt, modpls2$pp)

    modpls3 <- plsRglm(
      yhyptis[-c(1, 11, 17, 22)],
      Xhyptis[-c(1, 11, 17, 22), ],
      3,
      modele = "pls-glm-polr",
      dataPredictY = Xhyptis[c(1, 11, 17, 22), ]
    )
    modpls3$ValsPredictY
    cbind(modpls3$ValsPredictYCat, yhyptis[c(1, 11, 17, 22)])

    hyptis.bootYX3 <- bootplsglm(modpls2, typeboot = "plsmodel", R = 1000, strata = unclass(yhyptis), sim = "permutation")
    rownames(hyptis.bootYX3$t0) <- c("1|2\n", "2|3\n", "3|4\n", "Sabi\nnene", "Pin\nene", "Cine\nole", "Terpi\nnene", "Fenc\nhone", "Terpi\nnolene")
    boxplots.bootpls(hyptis.bootYX3, xaxisticks = FALSE, ranget0 = TRUE)
    plots.confints.bootpls(confints.bootpls(hyptis.bootYX3, typeBCa = FALSE), legendpos = "bottomleft", xaxisticks = FALSE)
    points(1:9, hyptis.bootYX3$t0, col = "red", pch = 19)

    hyptis.bootYT3 <- bootplsglm(modpls2, R = 1000, strata = unclass(yhyptis), sim = "permutation")
    rownames(hyptis.bootYT3$t0) <- c("Sabi\nnene", "Pin\nene", "Cine\nole", "Terpi\nnene", "Fenc\nhone", "Terpi\nnolene")
    boxplots.bootpls(hyptis.bootYT3, xaxisticks = FALSE, ranget0 = TRUE)
    plots.confints.bootpls(confints.bootpls(hyptis.bootYT3, typeBCa = FALSE), legendpos = "topright", xaxisticks = FALSE)
    points(1:6, hyptis.bootYT3$t0, col = "red", pch = 19)

## PLS Poisson Regression: Rock

The rock example compares a first-order Poisson PLSGLR model with a quadratic specification using interactions.

    data(rock)

    modpls <- plsRglm(
      area ~ .,
      data = rock,
      nt = 6,
      modele = "pls-glm-family",
      family = poisson(),
      pvals.expli = TRUE
    )
    modpls
    colSums(modpls$pvalstep)

    modpls2 <- plsRglm(
      area ~ .^2,
      data = rock,
      nt = 6,
      modele = "pls-glm-family",
      family = poisson(),
      pvals.expli = TRUE
    )
    modpls2
    colSums(modpls2$pvalstep)

    set.seed(123)
    cv.modpls2 <- cv.plsRglm(area ~ .^2, data = rock, nt = 6, modele = "pls-glm-poisson", K = 8, NK = 100)
    res.cv.modpls2 <- cvtable(summary(cv.modpls2))
    plot(res.cv.modpls2, type = "CVPreChi2")

    modpls3 <- plsRglm(area ~ .^2, data = rock, nt = 3, modele = "pls-glm-poisson")

    rock.bootYX3 <- bootplsglm(modpls3, typeboot = "plsmodel", R = 1000, sim = "antithetic")
    rownames(rock.bootYX3$t0) <- c("Intercept\n", "peri\n", "shape\n", "perm\n", "peri.\nshape", "peri.\nperm", "shape.\nperm")
    boxplots.bootpls(rock.bootYX3, indice = 2:7, xaxisticks = FALSE)
    plots.confints.bootpls(confints.bootpls(rock.bootYX3), legendpos = "topright", xaxisticks = FALSE)

    rock.bootYT3 <- bootplsglm(modpls3, R = 1000, stabvalue = 1e10, sim = "antithetic")
    rownames(rock.bootYT3$t0) <- c("peri\n", "shape\n", "perm\n", "peri.\nshape", "peri.\nperm", "shape.\nperm")
    boxplots.bootpls(rock.bootYT3, xaxisticks = FALSE, ranget0 = TRUE)
    plots.confints.bootpls(confints.bootpls(rock.bootYT3), legendpos = "topright", xaxisticks = FALSE)

# Creating Simulated Datasets

## Simulating PLSR Datasets

The original vignette used `simul_data_UniYX()` to generate synthetic datasets with a known number of latent components, then checked whether cross-validation recovered that number.

    dimX <- 24
    Astar <- 2

    simul_data_UniYX(dimX, Astar)
    dataAstar2 <- as.data.frame(t(replicate(250, simul_data_UniYX(dimX, Astar))))

    modpls2 <- plsR(Y ~ ., data = dataAstar2, 10, typeVC = "standard")
    modpls2

    set.seed(123)
    cv.modpls2 <- cv.plsR(Y ~ ., data = dataAstar2, nt = 10, K = 10, NK = 100)
    res.cv.modpls2 <- cvtable(summary(cv.modpls2))
    plot(res.cv.modpls2)

## Simulating Logistic Binary PLSGLR Datasets

### Continuous Covariables

The original PDF dichotomized the simulated response while leaving the predictors continuous.

    ydataAstar2 <- dataAstar2[, 1]
    XdataAstar2 <- dataAstar2[, 2:(dimX + 1)]
    ysimbin1 <- dicho(ydataAstar2)

    res <- plsR(ysimbin1, XdataAstar2, 10, typeVC = "standard", MClassed = TRUE)
    res$MissClassed
    res

    res$Probs
    res$Probs.trc

### Dichotomous Only Covariables

The last simulation in the original vignette was meant to mimic the structure of the allelotyping example by dichotomizing the whole generated dataset.

    bindataAstar2 <- as.data.frame(dicho(dataAstar2))
    resdicho <- plsR(Y ~ ., data = bindataAstar2, 10, typeVC = "standard", MClassed = TRUE)

    resdicho$MissClassed
    resdicho

    resdicho$Probs
    resdicho$Probs.trc

# Discussion

## Core Object Classes

The package exposes the following S3 classes for fitted models, cross-validation results, and summaries:

- `plsRmodel`
- `plsRglmmodel`
- `coef.plsRmodel`
- `coef.plsRglmmodel`
- `summary.plsRmodel`
- `summary.plsRglmmodel`
- `cv.plsRmodel`
- `cv.plsRglmmodel`
- `summary.cv.plsRmodel`
- `summary.cv.plsRglmmodel`
- `table.summary.cv.plsRmodel`
- `table.summary.cv.plsRglmmodel`

## Core S3 Methods

The corresponding S3 methods remain the main entry points for printing, summarizing, plotting, and predicting from these objects:

- `coef.plsRmodel`
- `coef.plsRglmmodel`
- `plot.table.summary.cv.plsRmodel`
- `plot.table.summary.cv.plsRglmmodel`
- `print.coef.plsRmodel`
- `print.coef.plsRglmmodel`
- `print.cv.plsRmodel`
- `print.cv.plsRglmmodel`
- `summary.cv.plsRmodel`
- `summary.cv.plsRglmmodel`
- `predict.plsRmodel`
- `predict.plsRglmmodel`
- `print.plsRmodel`
- `print.plsRglmmodel`
- `summary.plsRmodel`
- `summary.plsRglmmodel`
- `print.summary.plsRmodel`
- `print.summary.plsRglmmodel`

## Validation Examples

The applications note closes with a pair of validation examples: one comparing linear PLSR results with reference results from the literature, and one comparing ordinal logistic results for Bordeaux wine quality.

    data(Cornell)
    XCornell <- Cornell[, 1:7]
    yCornell <- Cornell[, 8]

    modpls <- plsR(yCornell, XCornell, 3)
    modpls
    modpls$uscores
    modpls$pp
    modpls$Coeffs

    modpls2 <- plsR(yCornell, XCornell, 4, typeVC = "standard")
    modpls2$press.ind
    modpls2$press.tot
    modpls2$InfCrit

    set.seed(12345)
    data(bordeaux)
    Xbordeaux <- bordeaux[, 1:4]
    ybordeaux <- factor(bordeaux$Quality, ordered = TRUE)

    modpls <- plsRglm(ybordeaux, Xbordeaux, 4, modele = "pls-glm-polr")
    modpls

    XbordeauxNA <- Xbordeaux
    XbordeauxNA[1, 1] <- NA
    modplsNA <- plsRglm(ybordeaux, XbordeauxNA, 10, modele = "pls-glm-polr")
    modplsNA

## Main Features of the Package

The central message of this applications note is that `plsRglm` provides a practical toolkit for high-dimensional, collinear, and possibly incomplete datasets, especially when generalized linear model extensions of PLS are required. The package combines model fitting, repeated cross-validation, bootstrap-based variable assessment, incomplete-data handling, and several response families in a single interface.

# Export Results to LaTeX

The original applications note included a short example using `xtable` to export cross-validation result tables to LaTeX. The exact table object comes from the microsatellite cross-validation summary; the example below recreates the same pattern in a standalone chunk.

    CVresults1 <- summary(cv.modpls.logit, MClassed = TRUE)

    resCVtab1 <- print(
      xtable::xtable(
        CVresults1[[1]][, c(1:6)],
        digits = c(0, 1, 1, 0, 0, -1, 4),
        caption = "Cross-validation results, $k=8$, part one"
      )
    )

    resCVtab2 <- print(
      xtable::xtable(
        CVresults1[[1]][, c(7:11)],
        digits = c(0, -1, -1, 1, 1, 3),
        caption = "Cross-validation results, $k=8$, part two"
      )
    )

    resCVtab1
    resCVtab2

# Session Information

    sessionInfo()
    #> R version 4.5.2 (2025-10-31)
    #> Platform: aarch64-apple-darwin20
    #> Running under: macOS Sonoma 14.7.1
    #>
    #> Matrix products: default
    #> BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
    #> LAPACK: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.1
    #>
    #> locale:
    #> [1] C/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
    #>
    #> time zone: Europe/Paris
    #> tzcode source: internal
    #>
    #> attached base packages:
    #> [1] stats     graphics  grDevices utils     datasets  methods   base
    #>
    #> other attached packages:
    #> [1] plsRglm_1.7.1
    #>
    #> loaded via a namespace (and not attached):
    #>  [1] dotCall64_1.2         spam_2.11-3           xfun_0.56
    #>  [4] bslib_0.10.0          lattice_0.22-7        vctrs_0.7.1
    #>  [7] tools_4.5.2           parallel_4.5.2        tibble_3.3.1
    #> [10] proxy_0.4-29          DEoptimR_1.1-4        cluster_2.1.8.2
    #> [13] pkgconfig_2.0.3       Matrix_1.7-4          som_0.3-5.2
    #> [16] RColorBrewer_1.1-3    lifecycle_1.0.5       compiler_4.5.2
    #> [19] fields_17.1           chemometrics_1.4.4    carData_3.0-6
    #> [22] permute_0.9-10        htmltools_0.5.9       maps_3.4.3
    #> [25] class_7.3-23          sass_0.4.10           yaml_2.3.12
    #> [28] Formula_1.2-5         pillar_1.11.1         car_3.1-5
    #> [31] jquerylib_0.1.4       MASS_7.3-65           cachem_1.1.0
    #> [34] bipartite_2.23        plsdof_0.4-0          vegan_2.7-2
    #> [37] rpart_4.1.24          boot_1.3-32           abind_1.4-8
    #> [40] mclust_6.1.2          nlme_3.1-168          robustbase_0.99-7
    #> [43] pls_2.9-0             network_1.20.0        digest_0.6.39
    #> [46] mvtnorm_1.3-3         splines_4.5.2         pcaPP_2.0-5
    #> [49] fastmap_1.2.0         grid_4.5.2            cli_3.6.5
    #> [52] magrittr_2.0.4        e1071_1.7-17          rmarkdown_2.30
    #> [55] igraph_2.2.2          otel_0.2.0            nnet_7.3-20
    #> [58] sna_2.8               coda_0.19-4.1         evaluate_1.0.5
    #> [61] knitr_1.51            viridisLite_0.4.3     mgcv_1.9-3
    #> [64] lars_1.3              rlang_1.1.7           Rcpp_1.1.1
    #> [67] xtable_1.8-8          glue_1.8.0            rstudioapi_0.18.0
    #> [70] jsonlite_2.0.0        R6_2.6.1              statnet.common_4.13.0

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